As an in-situ test method for evaluating durability of a newly-built or existing concrete structure, a non-destructive inspection or investigation directly measuring the mass transfer resistance is known in the art. In a constructed concrete structure, the resistance is reduced, owing to cracks, placing joints, construction joints and so forth, and therefore, the non-destructive inspection or investigation for investigating reduction of the resistance in the in-situ test is effective in evaluating the durability of the concrete structure.
An air permeability test focusing on transfer of air, or a water permeability test or a water absorption test focusing on transfer of water are known as a method for directly measuring the mass transfer resistance. It is considered that deterioration of concrete relates to chemical reaction, physical action and so forth in which water is participated. For instance, a case is exemplified in which corrosion of steel materials in reinforced concrete does not occur in a condition of extremely dry environment, even if carbonation of concrete progresses to the extent that the carbonation reaches the steel materials. Therefore, it is important to grasp the transfer of water for clarifying the deterioration of concrete.
A water pressure acting on an actual and usual structure is a relatively low pressure, which acts on its surface owing to rainfall and so forth. Pore diameters and a mass transfer mechanism dominating the mass transfer differs, depending on variation in fluid pressure acting on the concrete. Therefore, the test is preferably carried out under a condition equivalent to the ambient environment surrounding the actual structure, that is, under a condition that a relatively low pressure, such as a water head of approximately 200-300 mmAq, acts on the concrete surface. In the water permeability test, however, the water pressure of several newtons per mm2 is usually imposed on the concrete surface. This may increase the water permeability after the water permeability test, owing to destruction of a concrete texture. Therefore, in general, it is considered that the water absorption test is effective, wherein the concrete surface is merely subjected to a water pressure corresponding to a pressure naturally acting on the concrete surface during rainfall.
“British Standard 1881-5” “Method of Testing Concrete” “Initial Surface Absorption Test” (non-patent literature No. 1), which is referred to as “ISAT” hereinafter, is known as a surface water absorption test for measuring an amount of water absorbed through a concrete surface by concrete. In this test method and its test device, the amount of absorbed water is measured in a condition that the water pressure of 200 mmAq acts on the concrete surface. The water pressure of 200 mmAq is a pressure slightly higher than the water pressure acting on the concrete surface during heavy rainfall. Further, in “An automated method for the measurement of surface water absorption into permeable materials” (non-patent literature No. 2), the measuring method is disclosed, in which water absorption properties of water permeable materials are measured with use of a capillary tube and a sophisticated optical measuring device. Furthermore, a water permeability test method with respect to coating materials for building finishing works is disclosed in “JIS A6909-2003 coating materials for building finishing works” (non-patent literature No. 3). The test of JIS A6909-2003 is a water absorption test or water permeability test for paint and so forth, wherein the test is conducted with use of a specimen coated with the paint and so on to be applied to the concrete surface or the like.
However, the test methods and the test devices as set forth above are merely methods and devices for conducting measurement of water absorption properties or water permeabilities of horizontal surfaces of concrete specimens in laboratories. In other words, they are not the test methods and the test devices for in-situ measurements of water absorption properties or water permeabilities of vertical surfaces and so forth with respect to actual structures, which are land fixtures affected by external factors (ambient environmental conditions, construction conditions and so forth). That is, the test devices and methods disclosed in the non-patent literatures Nos. 1 to 3 are not intended for in-situ non-destructive tests for investigating the surface water absorption properties of the actual structures. Further, it may be considered that samples extracted from the actual structures are tested for investigating their water absorption properties in accordance with the test methods as disclosed in the non-patent literatures Nos. 1 to 3. However, as regards the water absorption test method for the actual structures newly-built, it is difficult to employ the test methods involved in extraction of the specimens therefrom. Further, even in a case where the specimens are extracted from the existing structures built in the past, the positions or locations of the structures, from which the specimens can be extracted, are limited. In addition, it is necessary to repair or mend the structures after the tests.
Further, a test method accompanying drilling of a hole in an actual structure is known in the art as a conventional water absorption test method. However, such a test is an in-situ test resulting in damage of the actual structure. Therefore, this is not the non-destructive test of the actual structure.
On the other hand, water absorption test devices are disclosed in non-patent literatures Nos. 4 and 5, wherein water absorption tests are conducted with respect to existing concrete structures with its surface coated with silane system water-repellent agent. Each of the test devices disclosed in the non-patent literatures Nos. 4 and 5 is so arranged that a circular cup with a vertical pipette in a form of tube is secured on a wall surface of an actual structure and that an in-situ measurement of an amount of water absorbed by a concrete surface thereof is carried out by measuring reduction of water filled in the cup.
Furthermore, an in-situ test device with a simple arrangement is known in the art, which comprises a water absorption cup of a small size fixed to a vertical concrete surface without destruction thereof, wherein a base plate of the cup is fixed to the vertical concrete surface by vacuum pressure.